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Timing light and Tachometer

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  • #16
    Hey Tod,

    The aftermarket digital tachs will be looking for 1 spark for 2 revs, a conventional automotive setup, but we have 2 sparks for 2 revs, so the tach would be counting 1 to many revs, so that's why you need to divide by 2 to get the TRUE rpms per the tach readout. You are right in how YOU are counting the rpms and sparks, but the tach would not be! Get it, got it, good!
    T.C.
    T. C. Gresham
    81SH "Godzilla" . . .1179cc super-rat.
    79SF "The Teacher" . . .basket case!
    History shows again and again,
    How nature points out the folly of men!

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    • #17
      The tach has a X 2 built in to it to read correctly with 1 spark per two revs. Give it 1 spark per each rev and it reads 2 x the actual revs. So divide by 2.

      Steve
      80 XS1100G Standard - YammerHammer
      73 Yamaha DT3 - DirtyHairy
      62 Norton Atlas - AgileFragile (Dunstalled) waiting reassembly
      Norton Electra - future restore
      CZ 400 MX'er
      68 Ducati Scrambler
      RC Planes and Helis

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      • #18
        The timing light I bought has a feature built into it for 2 cycle and 4 cycle for the digital tach, the instructions say to use the 2 cycle setting for wasted spark distributer-less systems. It worked very well for me.
        Thanks again folks!

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        • #19
          Yea, that works too.

          Steve
          80 XS1100G Standard - YammerHammer
          73 Yamaha DT3 - DirtyHairy
          62 Norton Atlas - AgileFragile (Dunstalled) waiting reassembly
          Norton Electra - future restore
          CZ 400 MX'er
          68 Ducati Scrambler
          RC Planes and Helis

          Comment

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